Canadian Journal of Anesthesia, Vol 9, 479-487, Copyright © 1962 by Canadian Anesthesiologists' Society

The Electroencephalogram after Cardiac Arrest

¹ Department of Anaesthesia, University of Western Ontario, and Victoria Hospital, London, Ontario

There is no specific E.E.G. pattern that indicates with certainty irreversible brain damage. Following a short period of cerebral ischaemia, the E.E.G. shows a definite pattern of recovery. Failure of this recovery pattern to occur may indicate brain damage, as does the appearance of a "file pattern" and of convulsive discharges. However the whole recovery must be viewed as a functional process,and while a single E.E.G. record may be of little significance, frequent recordings can aid in the prognostic assessment of the case.

There is a relationship between the duration of ischaemia and the time interval between restoration of blood flow and return of function. The duration of this latency of recovery is in turn related to the total recovery time and this is proposed as a more suitable basis for assessing the patient's chance of recovery than an estimate of the time of ischaemia. The use of hypothermia is probably indicated if the electrical activity has not returned after 15 minutes.₃ It appears possible that apart from the E.E.G. a similar relationship could be established using the return of reflex activity to determine this latency of recovery, thereby making an assessment of the expected speed of recovery possible.

However, attention is drawn to the observation that a considerable reflex activity may return temporarily after several hours in spite of irreversible damage of the brain.

Note:
Presented at the annual meeting of the Canadian Anaesthetists' Society, Montebello, Quebec, May 14–17, 1962.